docs: def normalize_bins(self, inplace: bool = False) -> "HistogramCollection":
          """Normalize each bin in the collection so that the sum is 1.0 for each bin.
  
          Note: If a bin is zero in all collections, the result will be inf.
          """
          col = self if inplace else self.copy()
          sums = self.sum().frequencies
          for h in col.histograms:
              h.set_dtype(float)
              h._frequencies /= sums
              h._errors2 /= sums ** 2  # TODO: Does this make sense?
          return col